1. Field of the Invention
This invention relates to delineators used for highway marking. More particularly, the present invention relates to an improved, tubular highway delineator which is flattened and fused together at the top such that rain water and debris may not enter the tube.
2. State of the Art
Highway construction and signage entail the installation and use of delineators to mark the edge of the safe roadway (see FIG. 2), to mark the location of nearby hazards, and to temporarily mark lane division stripes in construction zones or in areas with changeable lane configurations such as reversible commuter lanes or near toll collection booths (see FIG. 3). When properly placed, highway delineators help guide motorists and provide advance warning of potential hazards. Typical delineators comprise a post with a reflector attached near its top. The post is embedded in the highway embankment, or attached to a base fixture in the paved roadway or in the embankment, and is of a height such that it is visible by the ordinary driver from a safe distance, depending on the design speed and geometry of the particular section of roadway. An attached reflector allows the delineator to be visible at night or during low visibility times of the day. In locations where heavy snowfall is anticipated, highway delineators may be six or eight feet tall or more, to allow wintertime visibility when snow accumulation would cover a delineator of ordinary height.
In the past, delineator posts have been made of wood and metal. However, these can be a severe hazard when vehicles collide with them at higher speeds. Subsequent repair or replacement is costly, and also exposes maintenance personnel at risk with high speed traffic. More recently, impact resistant delineators made of lightweight polymers such as polyvinylchloride (pvc), polypropylene, and high density polyethylene (hdpe) have been used widely because they are inexpensive to manufacture, present less of a safety hazard, are easier and cheaper to transport, yet can still meet the design requirements highway designers demand. Composite posts of resin and fiber reinforcement have provided an additional category of delineators which incorporate column stiffness and lateral flexibility for impact. This wide variety of compositions and geometric shapes has produced a broad spectrum of delineator devices which are specifically designed for particular purposes.
One particular class of delineators referred to as high impact posts are positioned in congested traffic areas and are designed to take repeated impacts. These posts are generally made of softer plastics such as thermoplastic polymers. The primary design requirements of this class of highway delineators include sufficient strength to resist repeated buffeting forces of wind and recurring bumper and tire impacts in the locality of installation. In addition, they must be sufficiently durable to resist degradation due to sunlight, heat, cold, rain, snow, wind, salt, roadway oils, and other anticipated highway conditions.
High impact delineators are represented by the structure shown in FIGS. 1 and 2 depicting a conventional lightweight tubular highway delineator. It is comprised of a vertical, thermoplastic tube 20 that is embedded in a highway embankment 42, with a reflector 28 attached near its top. Alternatively, the bottom end of the delineator may be attached to a base fixture that is embedded in a highway or highway embankment, or is coupled to a ground-mounted base member 50 as shown in FIG. 3. Conventional highway delineators typically have a round or nearly round cross-section as depicted. A round cross-section is desirable because it provides uniform bending strength relative to transverse forces from any direction, and thus gives the delineator uniform resistance to wind from any direction. However, a round cross-section limits the visual aspect and surface exposure for reflective decals, making it less visible than desired. For example, a rounded surface reflects incident light back in all directions, resulting in a relatively small amount of light reflected back to a motorist from automobile headlights at night.
An additional problem associated with tubular delineators arises with the attachment of a reflective decal at an upper end of the tube. Those delineators which have been partially flattened at the upper end to provide the required surface exposure have often been capped with an elliptical cover designed to maintain the flattened shape. When the cap is removed by impact or vandalism, the restraining influence of that shape is lost, and the tube tends to restore toward its circular shape. This not only reduces the width of the exposed surface, often resulting in loss of compliance with specifications, but also weakens the bond of the reflective material. Specifically, as the curvature of the upper tube member shifts to a shorter radius, the reflector material tends to peal away from the outer tube surface. Further weathering can quickly degrade the reflector adhesive, resulting in ineffective reflection or even total separation of the reflector from the tube.
To provide greater visibility, some delineators 54 have been produced with a flat web section 56, as illustrated in FIG. 4. Flat delineators provide the advantages of high visibility and minimal potential collision hazard, but tend to be stiffer and have lower sheer strength. In high impact areas, the larger bending radius of the stiffer materials is subject to elastic failure, particularly with tire impacts.
To address this problem, tubular delineators 60 have been designed with a round cross-section 62 in their lower portion where high elastic stress are applied, with a flattened or oval or elliptical cross section 64 near the top. This combination provides enhanced impact response with the lower tubular design, but increased surface exposure in the region where the reflector 28 is attached. FIG. 5 depicts the top portion of typical delineators with an oval or elliptical cross-section 66 near the top. An oval or elliptical configuration has the advantage of providing a broader surface for attachment of the reflector, and also provides a broader aspect which makes the delineator more visible when it is installed with the flatter surface facing an on-coming driver.
However, these configurations still present several problems that have not been solved in the prior art. A simple tubular delineator, as depicted in FIGS. 5 and 6, whether circular or elliptical, is open at the top, allowing rain, snow, and debris to enter the tube. This can cause several problems. Rain or snow water that enters can freeze and burst the tube or dislodge it from its base. Debris or water that gets into the tube or from the tube into the base can also make temporary delineators difficult to install or remove. The accumulation of debris within the base of the tube tends to lessen the resilience of the tube after impact, and may increase the splitting or breaking of the tube in view of the particulate rock within the tube interior. Upon impact, such debris tends to fracture or split polymer material, greatly weakening its sheer strength and its resilience.
Some conventional tubular delineators attempt to solve these problems by placing a cap 68 over the top of the tube, as in FIG. 5. However, this solution has several disadvantages. The cap may fall off and become lost, thus not performing its intended function. This is particularly true with a vehicle impact, which usually rips the cap free from its mounted position. It also increases the manufacturing cost of the delineator, and introduces an additional maintenance expense.
Additionally, an oval or elliptical cross-section still does not provide the broadest aspect for reflectivity. A preferred delineator will incorporate the mechanical strength and resilience advantages of a circular or nearly circular cross section in its post, while providing the visibility advantages of a flat reflector, and preventing the introduction of water and debris into the tube. The following specific discussion on the prior art figures will assist the reader to appreciate the significance of the present invention.
FIG. 1 provides a front view of a typical highway delineator 20, which is generally comprised of an elongated tube 22, typically of circular cross-section as depicted, having a top end 24, and a bottom end 26, and a reflective marker 28 attached to the top of the tube. In a typical installation, the bottom end 26 is embedded into the ground some suitable distance 32 below the surface of the ground 30. In many conventional delineators, the top end 24 is somewhat flattened for some distance 29 from the top to create an oval or elliptical cross section, with the a reflective marker 28 attached to the flatter or broader side of the cross-section. This provides a larger visual aspect for the reflective marker 28.
FIG. 2 shows a roadway cross section depicting one typical installation of a highway delineator 20 alongside a roadway 34. In this installation the delineator 20 is located some distance 40 from the edge 37 of the traveled roadway 34, typically located near where the usable shoulder slope 38 transitions into the generally steeper roadway embankment 42. As in FIG. 1, the bottom end of the delineator is embedded some suitable distance 32 into the roadway embankment. FIG. 2 depicts this installation adjacent to a roadway 34 constructed with pavement 36, but delineators may also be used adjacent to unpaved roads.
FIG. 3 shows a surface mounted, alternative installation of a typical highway delineator 20 between lanes 46 of a roadway 44. In this installation, the delineators 20 are usually either connected to a suitable base support fixture at 50, or are inserted into holes in the pavement at the same location. The delineators are typically located in line with the lane stripes 48, and are situated some suitable distance 52 from each other. Reflective markers 28 may be attached to both front and back of the delineators 20, so as to be visible to traffic from both directions. One embodiment of the present invention defines a method of use of the described highway delineator which is compatible with the installations depicted in FIG. 2 and FIG. 3.
FIG. 4 shows a perspective view of the top of one type of conventional flat highway delineator 54. This type of delineator is typically comprised of a solid shaft 56 of thermoplastic material having a constant cross-section 58, with a reflector 28 attached to its flat face. Because of its broad aspect, thin cross-section, and soft polymer construction, this delineator is highly visible, but quite weak. Fiber reinforced, thermosetting materials may also be used in this configuration, and give enhanced stiffness; however, such composite delineators have a larger bending radius and are not as practical for high impact areas.
FIG. 5 shows a perspective view of the top of a conventional flattened tubular highway delineator 60 which is generally comprised of an elongated tube 62 which has a circular or other suitable cross-section in its lower end as shown. The top end, however, is flattened to an oval cross-section, 64 so as to allow a reflective marker 28 to be affixed to the broad face of the tube in the flattened region near its top. In some embodiments of this type of conventional delineator, the opening 66 in the top of the tube is covered by a cap 68, to prevent water or debris from getting inside the tube.
FIG. 6 shows an alternative perspective view of the top of a conventional elliptical highway delineator 70, that is fastened together by a mechanical fastener 78 at its topmost extreme. The cross section of the top part of the shaft 72 is typically oval or elliptical, as in the alternative of FIG. 5, and has a reflective marker 28 attached to its broad face. The lower portion of the tube 72 is typically of circular cross-section, as shown. The fastener 78 causes the cross-section at the top 74, to deform and change the opening 76 in the top of the tube into two separate openings 76'. This configuration still has the disadvantage of allowing water or debris to enter the top of the tube.